Design: Thirty five consecutive patients referred for commencement of parenteral nutrition (PN) were included. Serum leptin and IGF1 were measured prior to starting PN. Electrolytes, liver and renal function tests were measured before and daily for one week after initiating PN. The primary outcome was a decrease in phosphate on day two or three after initiating PN. A 'Refeeding Index' (RI) was defined as leptin x IGF1 divided by 2800 to produce a ratio of 1.0 in patients who are well nourished.